In Holding Their Breath: How the Allies Confronted the Threat of Chemical Warfare in World War II, M. Girard Dorsey makes significant contributions to multiple fields, including military history, diplomatic history, the history of arms control, and the history of the Second World War. She provides the most thorough examination to date of the reasons why the United Kingdom, the United States, and Canada refrained from attacking their enemies with chemical weapons during the Second World War, and she documents their sustained efforts to discourage the Axis Powers from using them. Adopting an ambitious transnational scope, Dorsey analyzes the complex diplomatic and military relationships that shaped Allied gas policy. She also demonstrates a deep familiarity not only with a wide range of primary sources, including oral histories, diplomatic correspondence, and cabinet minutes, but also the vast historiographies of the fields with which she engages.

Dorsey frames this study through comparisons with the unsuccessful international efforts to prevent the use of chemical weapons that took place in the decades immediately preceding the First World War, a subject that she explored in a more limited way in her chapter in War, Peace and International Order? The Legacies of the Hague Conferences of 1899 and 1907, ed. Maartje Abbenhuis, Christopher Ernest Barber, and Annalise R. Higgins (2017, 86-102). One of the limitations of the Hague Conventions, Dorsey shows, is that their language was quite narrow, which allowed German leaders to claim in 1915 that releasing chlorine from fixed canisters did not violate the letter of international law, even if it flew in the face of its spirit.

The decision to keep the chemical genie in the bottle during World War II was something that took contemporaries by surprise, particularly considering the clear failure of international law to prevent the extensive use of toxic chemicals on the battlefields of the First World War (a topic that Dorsey explored in her previous monograph, A Strange and Formidable Weapon: British Responses to World War I Poison Gas [2008], writing as Marion Girard). In Holding Their Breath, Dorsey demonstrates that memories of the gruesome effect of chlorine gas, phosgene gas, and mustard gas on the Western Front shaped most people’s expectations of what a future war would bring. Even more frightening, at least for civilians, were predictions that enemy bombers would drop thousands of tons of poisonous bombs on towns and cities. The Second World War was the deadliest conflict in human history, full of unprecedented horrors, including the Holocaust, firebombing, and the detonation of nuclear weapons. The extent of suffering would have been far greater had chemical weapons been released on a massive scale.

How was this added nightmare avoided? This is the fundamental question at the heart of Dorsey’s book, which she answers by arguing that no single explanation can account for the absence of poisonous chemicals among the weapons dropped from airplanes and shot from artillery during this conflict. Despite the Geneva Gas Protocol of 1925 and later declarations by both Britain and Nazi Germany that neither would initiate chemical warfare against each other during the Second World War, Dorsey shows that the belligerents remained convinced that their enemies would violate these promises if they ever perceived the benefits to outweigh the costs that such a move would entail. To deter this from happening, each of the combatants walked a fine line. On the one hand, they sought to develop a credible chemical arsenal to deter their foes, but on the other hand, they worked hard to assuage their enemy’s fears that they might be preparing a surprise first strike with toxic chemicals.

Had Germany attempted a ground invasion of mainland Britain in 1940 or early 1941, Churchill was prepared to use chemical weapons to repel it. Later in the war, when Hitler directed his so-called vengeance weapons, the V1 and V2, against Britain, Churchill contemplated responding with chemical attacks on German cities. Dorsey also examines American policies toward Japan in the final months of the war. Both FDR and later Truman showed little hesitation in employing extremely destructive weapons—not only atomic bombs, but also incendiary weapons and conventional high explosives. Had the Manhattan Project failed to produce a functioning atomic bomb in 1945, suggests Dorsey, the world’s first use of NBC (nuclear, chemical, and biological) weapons against major population centers might well have been a chemical attack by the US against Japan.

In addition to providing a deeply researched portrait of chemical weapons strategy and diplomacy during the Second World War, Dorsey discusses its legacies, including the Chemical Weapons Convention of 1993, which, when it came into force in 1997, finally required signatories to forswear the development, acquisition, transfer, and use of chemical weapons. Holding Their Breath is an exemplary piece of scholarship, marked by painstaking research, reasoned argument, clarity of expression, and astute interpretation of a wide array of sources.